Put a sugar cube into each of 6 Champagne flutes or wineglasses. Douse each cube with 1/2 tsp. bitters. Top with Champagne and serve immediately.
Note: Nutritional analysis is per cocktail.
No reason to bust open the good stuff here. The subtle flavors and fine bubbly texture of high-quality Champagne would be lost once mixed with sugar, so feel free to use less-than-stellar sparkling wine in these cocktails.